[Music] hi everybody welcome back to med school eu my name is andre and in today's educational video we will be covering one of the last topics of the biology section of the imad specifications and that is homeostasis now in today's video we are going to talk about the endocrine system and have a bit of an introduction to hormones so let's first talk about what is hormonal communication and how does it actually work well we previously discussed our nervous system and the nervous system is fast but it is very energy expensive in terms of that it is able to communicate messages from one part of the body to another part of the body for example like the brain communicating messages to the muscles in order to move or communicating messages to the heart in order to pump with a certain speed so all of those are communicated through the nervous system because we need fast response time but movement of such messages is typically very very energy expensive and so the body cannot use solely the nervous system in order to convey its messages there are other means of communication within the body to relay messages to other parts in order to do their function and today we are going to introduce one of these other methods and that is through the endocrine system now in terms of the endocrine system it is a means of communicating with parts of the body and eliciting responses through hormones so these hormones are going to be the communicating molecules that will communicate between one part of the body with another part of the body and we have seen this in the previous lectures we just haven't named those things as and as part of the endocrine system but that is what we were studying so for example when we studied about the glucose homeostasis and when we studied about adh and and maintaining the water homeostasis within the body that is all part of the endocrine system because it does not go through the nervous system yes the nervous system is involved in terms of sending impulses to the endocrine system to release those hormones however the endocrine system will be the one that is activating the effectors meaning the the kidney uh becoming more permeable to water and absorbing more water in terms of water balance from adh which is a hormone and in terms of glucose control that would be the glucagon and the insulin so we talked about these things in the previous lectures about the endocrine system however the endocrine system is slow in terms of response time compared to the nervous system but it is inexpensive in terms of energy expenditure now these hormones in the endocrine system will typically be released by glands so what is a gland well a gland is a group of cells that produces and secretes one or more substances and these substances are most commonly referred to as hormones so there will be releasing other substances depending on the bodily needs and what the gland really does but in terms of the endocrine system we will typically be talking about the release and the production of hormones from the glands now there's two types of glands within our body there's the exocrine glands that have ducts and there's endocrine glands so since it's the endocrine system we'll be talking about endocrine glands now the endocrine glands secrete directly into the blood meaning that they have no ducts so the hormones that will be produced and secreted are going to be released directly into the blood and then the blood will obviously circulate and it will bind to the appropriate cells that it will activate and then the the cell will be the the effector or the group of cells will be the effectors as we've seen with glucagon and insulin and the adh so the all of those three hormones that we have discussed previously they are released into the blood and they're going to circulate around in our circulatory system and they will only attach and have an effect on the cells that have receptors for them and so here is the endocrine system and you can see how many different organs and and organ system it involves so we've got the pineal gland that is located in the brain pituitary in the hypothalamus that's something that we have discussed already and then we've got the thyroid and the parathyroid glands so these glands are going to be very important in releasing different types of hormones as well the thymus the training center the university for the immune cells the thymus will also be releasing a hormone pancreas we've talked about pancreas releasing insulin and glucagon adrenal glands releasing also planting plenty of hormones that we're going to discuss in the next slide and the testes in in terms of males will be releasing uh hormones like testosterone whereas in the female all the parts will be the same except for females having the ovary as being the sexual organ that produces hormones and the placenta that will only occur during pregnancy now before we move on to the types of hormones and all the different hormones that are involved within the human body i just wanted to classify them into two separate types and what really are hormones simply put hormones are cell signaling molecules well technically hormones can be divided into many various types of of hormones depending on where they come from what their structure looks like are they peptide or the fat but i'm just going to divide them into into generally two types ones that are water soluble and ones that are lipid soluble because they will have different effects on the cells and and how they enter the cells or not enter the cells what they do to the cell and how they are functioning as the signaling molecules will differ depending on whether they're water-soluble or lipid-soluble so first talking about water-soluble hormones and water-soluble hormones are typically peptide hormones meaning that they are protein they're made up of proteins so like we saw with adh was a peptide hormone it is water soluble and as well as the insulin and glucagon they're all peptides generally speaking and they will be water soluble and so if they're water soluble they will not be able to penetrate the cell membrane they will not enter the cell membrane they will remain on the outside of the cell and they will typically attach to receptors just like the adh the glucagon and the insulin they all have receptors on different cells to attach to and what they're going to do is cause a signaling cascade now if we're talking about the second type and that is going to be our lipid soluble and these are typically going to be classified as steroid hormones now these hormones are obviously since they are lipid soluble they will not be dissolving in the blood and they will be traveling around and they will typically enter inside the cell so they will penetrate the membrane because membrane remember is a lipid it's a it's a phospholipid bilayer and so if it is lipid soluble then it will be able to pass the lipid membrane since they are nonpolar together but because the other ones are peptides and they're water soluble they're polar and they're not able to pass the membrane because the membrane is nonpolar and so these lipid soluble hormones the steroids are going to be passing along the membrane and they will be acting inside of the cell and typically they're either going to attach to a nucleus and and they will have effects on certain genes and they will stimulate the cell to produce certain proteins from those genes marking them as as being these signaling molecules or they're going to attach to it and be like markers to suggest to the cell that hey you need to produce these types of hormones or these types of proteins however there's obviously a lot more involved in it but this is just the gist of dividing the hormones into several types now finally i just wanted to show the chart here of the endocrine system and all of the hormones that are involved the types of hormones and the action they produce go over all of these hormones and i suggest you know the action of these hormones and how they typically work i'm not going to go through it in detail here however this is the chart for you to use in order to memorize these things so this concludes the lecture for today and in the next one we are going to take a look at the homeostasis of the menstrual cycle [Music] you